American nuclear pulse orbital launch vehicle. The final iteration of the Orion design was a nuclear pulse propulsion module launched into earth orbit by a Saturn V. The 100 tonne unit would have had a diameter of 10 m to match that of the booster. This would limit specific impulse to 1800 to 2500 seconds, still two to three times that of a nuclear thermal system.

A second launch would put a 100 tonne Mars spacecraft with a crew of eight into orbit. After rendezvous and checkout, the combined 200 tonne spacecraft would set out on a round trip to the Mars - total mission duration as little as 125 days!

Orion Nuclear-pulse drive launch vehicle seriously developed by General Atomics in the United States from 1955-1965. The design allowed vast payloads of hundreds of tons to be hurled to the planets. By 1958 the Orion team saw themselves in direct competition with Von Braun's chemical rockets. They hoped to a land a huge manned expedition on Mars by 1964 and tour the moons of Saturn by 1970. However politically NASA would not argue for the exception to the 1963 Nuclear Test Ban Treaty necessary to allow firing of nuclear explosions in space. More...